The present invention is directed to an apparatus and method for measuring the crevice gap clearance in a heat exchanger and more particularly for steam generators used in nuclear power plants.
Currently many steam generators used in nuclear power plants suffer corrosion problems in the gap between a heat exchange tube and a tube support plate. Buildup of these corrosion products has many bad side effects including denting of the tube, or constricting it to a smaller diameter which causes cracks and developing leaks. Thus in order to obtain an early warning of the onset of denting, etc. it is desirable to measure the clearance between the tube outer diameter and the tube support plate. Ultrasonic and eddy current techniques have been attempted but have not proved satisfactory.
Moreover, it may also be possible to chemically clean or reverse the buildup of corrosion. Thus a technique for indicating when chemical cleaning should be applied and thereafter measuring the effect of such chemical cleaning is also highly desirable.